I had the same question several years ago after buying a box of standard LRP's and upon opening finding I had 1000 magnum LRP's. So I asked this question about rifle primers and was given enough positive answers to test them in all of my LRP rifles. I reduced the start charge weight by .5 grains and worked up and I ended up back at the start charge. I didn't do this for pistols but I understand it is the same principle. I wouldn't have found this out if they would let us return unopened primers, but that isn't allowed.